In such a device, the heat is generated by absorbing a refrigerant vapor as a solvent (such as water) into a flowing high salt concentration solution such as a lithium bromide solution whereby heat is transmitted to a fluid which flows internally of the pipe or pipes. Alternatively heat is transmitted from a hot fluid flowing internally of the pipe or pipes to a solution which flows along the outside surface of the pipe wall to produce the vapor which surrounds the transmission pipes from the solution flowing down the external surface of the pipe or pipe outer wall.
FIG. 1 shows an example of a conventional device of this type wherein a cylindrical transmission pipe 11 has a spiral fins 12 attached to the outer surface or periphery 13 of the transmission pipe 11.
FIG. 2 shows a pipe 11 arranged vertically, in a heat and mass transfer device wherein a high salt concentration solution 14 is sprayed from a nozzle (not shown) against the pipes indicated generally at 11 permitting the solution to leak down along the outer surface 13 of the pipe wall with the wet heat produced by the solution absorbing vapor surrounding the pipes 11. The heat is transmitted through the pipe wall to the interior of the pipe and thus to the fluid flowing axially through the pipes 11.
FIGS. 3-7, inclusive, show another conventional, prior art heat and mass transfer device corresponding to Japanese Patent No. 59-19074 which is an improvement over the prior art shown in FIGS. 1 and 2. The device shown in FIGS. 3-7, inclusive, uses tooth fins 18 or alternatively needle fins (not shown) which are fixed rigidly onto the external surface of pipe 11 with the tooth fins at some angle to the vertical axis of the pipe and directed upwardly. The rate of transmitting heat in the pipe 11 is increased because the sprayed solution is dispersed more uniformly around the tooth fins (or the needle fins). The tooth fins 18 shown in FIG. 5 are preferably arranged so as to overlap in the radial direction and the relationship between the individual fins may be regular or irregular. The fins are preferably formed by slitting or cutting a sheet metal fin plate or strip P from one edge inwardly towards the other edge to form cuts C and by wrapping the strip P about the periphery of the pipe 11, with fins extending outwardly and upwardly. Upon spraying of the high salt concentration solution 14 onto the outside of the pipe 11 the solution drops by gravity down through the fins 181-185 by filling the space between the fins and the surface of the pipe 11 in the longitudinal direction and by spreading among the fins circumferentially as shown in FIG. 6.
The heat and mass transfer device, FIGS. 3-7, inclusive, has improved characteristics for absorbing the vapor surrounding the pipe and an increase in the rate of heat transmission. However, such conventional prior art heat and mass transfer devices have not been designed, to applicants' knowledge to maximize the ability of the high salt concentration solution to absorb vapor by optimizing the inclination angles for the fins and/or the pitch between succeeding fin plate pieces based on analysis of performance.
FIG. 8 is a schematic illustration of an apparatus for effecting the flow of solution relative to a vertically oriented pipe provided with fins and forming a heat and mass transfer device in accordance with the prior art. Such apparatus consists of a finned pipe indicated generally at 82 with a spring balance 83 for maintaining the pipe in vertical upright position with its lower end centered within a upwardly open thermostatic bath 88. An upper vessel 84 concentrically surrounds the upper end of the pipe 82 and pipe 82 extends through a central hole 92 within the bottom of the upper vessel 84. A pipe 91 leads from the thermostatic bath 88 upwardly and to one side of the pipe 82 for transferring liquid from the thermostatic bath 88 to the upper vessel 84. A pump 90 is within pipe 91 along with a flow meter 89. The circulating solution flows by gravity through the annuler gap between pipe 82 and the hole 92 within the upper vessel 84 and falls down along the outside of the pipe 82 and over the fins 93 carried thereby.
It is therefore an object of the present invention to provide an improved heat and mass transfer device based on solving the best configuration for the fins and for their spacing relative to each other along the exterior of a vertical pipe for such heat and mass transfer device.